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While reading this article posted on dzone I found a snippet of JavaScript originally posted on Twitter by Marcus Lagergren . The following code apparently prints the string "fail" (![]+[])[+[]]+(![]+[])[+!+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]; This involves implicit type casting and I'm trying to understand how exactly this line is interpreted. I've isolated each character (![]+[])[+[]] prints "f" (![]+[])[+!+[]] prints "a" ([![]]+[][[]])[+!+[]+[+[]]] prints "i" (![]+[])[!+[]+!+[]] prints "l" I've also managed to break down the expressions returning each letter apart from "i" letter "f" ![] an empty array is an Object, which according to ECMAScript documentation, point 9.2 evaluates to true when converted to a boolean so this is false false+[] as per Point 11.6.1 both arguments of the binary + operator get converted to String, therefore we get "false"+"" , which evaluates "false" +[] a unary plus operator causes a ToNumber conversion followed by a ToPrimitive conversion if the argument is an Object . The result of such conversion is determined by calling the [[DefaultValue]] internal method of the object. In case of an empty array, it defaults to 0 . (ECMAScript Documentation, sections: <a href="http://www.ecm

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